Method of fabricating an abrasive wheel



Sept. 16, 1969 A. BLOCK 3,466,816

METHOD OF FABRICATING AN ABRASIVB WHEEL Filed March 7, 1967 2 Sheets-Sheet 1 Sept. 16, 1969 A. BLOCK 3,

METHOD OF FABRICATING AN ABRASIVE WHEEL Filed March 7. 1967 2 Sheets-Sheet 2 l/ea 6/064 Kara/1% 47702/V6KI United States Patent 3,466,816 METHOD OF FABRICATING AN ABRASIVE WHEEL Aleck Block, Los Angeles, Calif., assignor to Merit Products, Inc., Los Angeles, Calif., a corporation of California Filed Mar. 7, 1967, Ser. No. 621,262 Int. Cl. B24b 9/02 U.S. Cl. 51-336 12 Claims ABSTRACT OF THE DISCLOSURE The finished abrasive wheel comprises a cylindrical hub body with circumferentially spaced dove-tailed grooves on its outer circumference and with dove-tailed end portions of packs of abrasive leaves mounted in the grooves by an adhesive that not only solidifies the end portions of the packs but also bonds the end portions of the packs to the hub body. The fabrication procedure includes the steps of applying adhesive to the end portions of the packs, preforrning the end portions to dove-tailed configuration and then inserting the preformed end portions of the packs into the dove-tailed grooves of the hub body before the adhesive cures.

Background of the invention As taught by the Gillett Patent 3,212,219, it is old in the art of fabricating flap-type abrasive wheels to provide a hub body with circumferentially spaced dove-tailed grooves on its outer circumference and to preform packs of abrasive leaves to dove-tailed configuration for mounting in the grooves in a removable manner. When the abrasive leaves become unduly worn, side plates that cover the ends of the dove-tailed grooves are removed to permit new packs to be substituted for the worn packs.

One disadvantage of such a construction is the labor cost of removing the side plates, removing the worn packs of leaves, installing new packs of leaves and then reassembling the side plates. Such a renewal procedure not only involves labor cost but also, in many instances, incurs loss of production.

Another disadvantage arises from the fact that the dove-tailed grooves in the hub body in the above patent are triangular in cross section. Since the bottoms of the grooves are the widest parts of the grooves and are spaced substantially inward from the outer circumference of the hub body and since there is room for only a given number of grooves of a given width on a hub body of a given diameter, the number of grooves for which there is room may be inadquate if the hub body is of relatively small diameter. This limitation becomes apparent when the diameter of the hub body is reduced to 2" and becomes acute when the diameter is reduced below 1 /2.

The present invention not only eliminates the necessity of replacing the packs of leaves in an abrasive wheel but also solves the problem of mounting an adequate number of leaves on a hub body of relatively small diameter.

Summary of the invention One basic concept of the invention is that an inexpensive method of mounting the packs of leaves on a low cost hub body in a permanent manner instead of in a replaceable manner makes it economical to simply discard a worn abrasive wheel.

A second basic concept is that permanently bonding the dove-tailed ends of the packs of leaves to the surfaces of the dove-tailed grooves of a hub body provides adhesive anchorage in addition to the mechanical anchor age and thus lessens the burden placed on the mechanical dove-tailed anchorage. A third concept is that formlng a neck in a pack of the leaves by local compression causes the abrasive particles to interlock the leaves at the neck. These last two concepts make it possible to change the cross-sectional configuration of the grooves in a man ner to make it possible to increase the number of grooves on a hub body of a given diameter.

In the presently preferred practice of the invention, the dove-tailed grooves are of generally circular configuration in cross section instead of triangular configuration and in addition the maximum width of the grooves is reduced to make it possible to increase the number of grooves that may be provided in a hub body of any given diameter.

It is to be noted that the maximum width of a groove of substantially circular configuration is half Way to the bottom of the groove Whereas the maximum width of a groove of triangular configuration is at the bottom of the groove. Thus in a hub body of a given diameter, the maximum width of grooves of circular configuration is on a larger circumference than the maximum width of grooves of triangular configuration. This fact coupled with the fact that relatively narrow grooves of circular cross section may be used, makes it possible to mount a given desirable number of abrasive leaves on a hub body of smaller diameter than is possible within the teachings of the above patent.

In the fabrication procedure of the aforementioned patent, a low viscous resin is employed to bond the root portions of the leaves of a pack together and then a highly viscous resin is molded around the root end of the pack to form the required dove-tailed enlargement on the pack. In contrast, the fabrication procedure of the present invention employs a single resin on the root end of a pack and a pair of jaws compressively forms the dove-tail on the inner end of the pack to permit the dovetail to be inserted in a groove of the hub body before the resin cures. Thus the invention uses the dove-tailed grooves of a hub body itself as molds for the dove-tailed ends of the packs of abrasive leaves.

The invention achieves a substantial saving in omitting the step of pre-molding the dove-tailed ends of the packs. A further feature of the invention in this respect is that since the cured resin anchors the dove-tailed enlargements of the packs against lateral slippage in the dovetailed grooves of a hub body, further economy may be achieved by simply omitting the side plates that usually cover the opposite ends of the dove-tailed grooves to captivate the packs of leaves. In the preferred practice of the invention the fabrication cost is minimized by using a pair of jaws to form the dove-tailed enlargement on a pack of leaves and then aligning the pair of forming jaws with a dove-tailed groove in a hub member to permit a ram to transfer the formed pack of leaves to the dovetailed groove. With these cumulative savings in cost, it becomes economical to discard even a relatively large diameter abrasive wheel instead of taking time to remove the wheel.

Brief description of the drawings In the drawings, which are to be regarded as merely illustrative FIG. 1 is an elevational View of the presently preferred embodiment of the final product;

FIG. 2 is a transverse section taken along the angular line 22 of FIG. 1;

FIG. 3 is a diagrammatical view illustrating the step of drenching the hub body in a solvent;

FIG. 4 is a fragmentary elevational view illustrating the step of applying the adhesive or resin to the end of a pack of abrasive leaves;

FIG. 5 is a greatly enlarged fragmentary view of FIG. 1 showing how the root end of a pack of leaves is anchored in a dove-tailed slot of the hub body; and

FIG. 6 is a schematic view showing how the assembly of an abrasive wheel may be expedited by employing a ram to transfer packs of leaves from a pair of forming jaws to successive dove-tailed slots in a hub body.

Description of the preferred embodiment Referring to FIGS. 1 and 2, the finished abrassive wheel comprises a hub body 10 carrying an array of radially extending abrasive leaves. Each of the abrasive leaves 12 may be of a well known construction comprising a sheet of flexible material such as a suitable fabric with abrasive particles bonded to at least one of the two faces of the sheet. The hub body 10 comprises a single piece of metal of cylindrical configuration having a threaded axial bore 14 whereby it may be mounted on a screw threaded power driven arbor (not shown). The

abrasive leaves 12 are arranged in a plurality of packs 15 which are connected at their root ends to the hub body 10 by engaging dove-tailed slots 16 of the hub body. As

best shown in FIG. 5, the dove-tailed slots 16 are, in this v particular embodiment, of generally circular cross-sec tional configuration with narrowed entrances 18.

Each of the packs 15 is formed with a dove-tailed enlargement at its root end of a configuration complementary to the configuration of the dove-tailed grooves 16 of the hub member. As indicated in FIG. 5, each of the packs 15 is reduced in thickness at a region spaced from its root end to form a narrow neck that is dimensioned for snug fit in the entrance 18 of a dove-tailed slot 16. For this purpose the pack is locally compressed to such extent as to cause the abrasive particles on the face of one leaf to penetrate the leaf material of the contiguous leaf. A suitable adhesive material which is preferably an epoxy resin, forms a plastic dove-tailed enlargement 22 on the root end of each pack 15 and the resin not only penetrates into the spaces between the leaves 12 to bond the root ends of the leaves together but also adheres to the inner surfaces of the dove-tailed slot 16 to bond the pack directly to the hub body 10. In addition, a small extruded bead 24 of the epoxy resin may extend along at least one of the two edges of the en trance 18 of the dove-tailed slot to serve as further means for uniting the pack with the hub body.

The preferred method of fabricating the abrasive wheel is illustrated :by FIGS. 3 to 6.

FIG. 3 illustrates the initial step of employing suitable tongs 25 to immerse a hub body 10 in a suitable solvent 26, such as toluene, to clean the surfaces of the hub body and especially the inner surfaces of the dovetailed slots 16. The cleaned hub body 10 may then be mounted on a rotary spindle 26 that has a polygonal index enlargement 28 with a number of index surfaces 30 corresponding to the number of dove-tailed grooves 16 in the hub. body. A suitable leaf spring 32 presses against the successive index faces 30 to index the hub body 10 relative -to a forming jaw 34 that is suitably mounted on fixed structure. The fixed forming jaw 34 cooperates with a movable forming jaw 35 that swings about a hinge 35 and is controlled by a piston rod 38 of a pneumatic power cylinder 40.

When the two jaws 34 and 35 close together, they provide a forming cavity 42 that is of substantially the same cross-sectional configuration as a dove-tailed slot 16 ofahub body 10.

These abrasive leaves 12 are formed into packs 15" of the required number of leaves :and then the epoxy resin is applied liberally to one end of each pack. As shown in FIG. 4, a pack 15 may be held between the thumb and forefinger for this purpose while the epoxy resin is distributed across the end of the pack by the nozzle 44 of a suitable dispenser. The epoxy resin penetrates between the faces of the leaves adjacent the end 4 of the pack and in addition, as shown in FIG. 4 the epoxy forms a liberal layer 45 that envelops the root end of the pack.

While the resin is still fluent, the pack is placed between the two forming jaws 34 and 35 and the power cylinder 40 is energized to close the jaws thereby to crush the pack locally to form the previously mentioned neck in the pack. The forming jaws are then relaxed and a ram 46 actuated by a second pneumatic power cylinder (not shown) advances into and through the forming cavity 42 of the two jaws to slide the formed root end of the pack from the jaws into the aligned dove-tailed cavity 16 of the hub body. Sufficient epoxy adheres to the root end of the formed pack to completely fill the voids in the dove-tailed slot 16. In addition there is suflicient epoxy to form a previously mentioned extruded head 24 along at least one edge of the dove-tailed groove 16. The spindle 26 is then rotated to bring the next index face 30 into contact with the indexing leaf spring 32 and the operation is repeated. After all of the packs are assembled to a hub body 10 in this manner, the hub body is removed from the spindle 26 to permit curing of the epoxy resin.

It is apparent that a distinguishing feature of the invention is the concept of employing the dove-tailed slots 16 of the hub body 10 as means to mold dove-tailed enlargements on the inner ends of the packs 14. A special advantage of employing the slots 16 as molds for the inner ends of the packs is that the curing of the epoxy results in an efiicient adhesive bond between the epoxy and the inner surfaces of the dove-tailed grooves 20. Another distinguishing feature is the interlocking of the leaves by the penetration of the adhesive particles in the neck regions of the packs.

In the preferred practice of the invention the hub body 10 is an aluminum body that is formed by extrusion. Extruded aluminum bodies of this character may be pro duced in large quantities at relative low cost. The low cost of a hub body 10- together with the low cost of assembling the packs of leaves 14 to the hub body by the described fabrication procedure results in such a low total cost as to make it economical to discard a worn abrasive wheel instead of replacing the packs of abrasive leaves.

My description in specific detail of the presently preferred practice of the invention will suggest various changes, substitutions and other departures from my disclosure within the spirit and scope of the appended claims.

I claim:

1. A method of fabricating a flap-type abrasive wheel for use on a power driven arbor, characterized by the steps of:

providing a hub body of cylindrical configuration with an axial bore to receive the arbor and with a series of circumferentially spaced longitudinal peripheral grooves, said grooves being undercut to form peripheral entrances thereto that are substantially smaller in width than the maximum width dimension of the grooves;

providing leaves of flexible sheet material with abrasive particles bonded to at least one face of each leaf;

grouping the leaves in face-to-face relation to form packs of leaves;

applying adhesive to one end portion of each pack to cause a liberal coating of the adhesive to cling to the end of the pack and to adjacent surfaces of the opposite faces of the pack and to cause the adhesive to penetrate into the spaces between the leaves adjacent the end of the pack;

mounting the packs of leaves on the hub body by inserting the coated end portions of the packs edgewise into the open ends of the grooves of the hub body before the adhesive on the end portions cures; and permitting the adhesive material to cure to solidify the end portions of the packs and to form enlargements of cured adhesive on the end portions for dovetailed engagement with the grooves of the hub body and to bond the end portions of the packs to the surfaces of the grooves of the hub body to hold the packs against endwise slippage in the grooves.

2. A method as set forth in claim 1 which includes the' step of cleaning the surfaces of the grooves of the hub member prior to insertion of the end portions of the packs.

3. A method as set forth in claim 2 in which said cleaning step is carried out by drenching the hub body in a volatile solvent.

4. A method as set forth in claim 1 in which said adhesive is an epoxy resin.

5. A method as set forth in claim 1 which includes a. forming step carried out on each pack after the adhesive is applied to the end of the pack, said forming step comprising compressing said end portion of each pack across its thickness to a thickness to fit snugly in an entrance to a groove with the compression limited to a narrow zone that is spaced from the end of the pack by a dimension no greater than the radial distance from the bottom of a groove to the entrance of the groove thereby forming the pack with a reduced neck and thereby causing the leaves of the pack to engage each other in the region of the neck by penetration of the abrasive particles of leaves into adjacent leaves.

6. A method as set forth in claim 5 in which the step of compressively forming the end portions of the packs of leaves is carried out by gripping the end portions by a pair of jaws which define a forming cavity of the same general configuration as the peripheral grooves in the hub body.

7. A method as set forth in claim 6 in which the pair of jaws is aligned with the grooves of the hub body in succession and in which ram means is employed to displace the formed end portions of the packs of leaves from the pair of jaws into the grooves in succession.

8. In a flap-type abrasive wheel, the combination of:

a hub structure of generally cylindrical configuration having circumferentially spaced grooves on its outer circumferential surface with ends of the grooves open to at least one end of the hub structure;

said grooves being undercut to form peripheral entrances thereto smaller in width than the maximum width dimension of the grooves;

packs of leaves of sheet material with abrasive particles on at least one face of each leaf;

said packs corresponding to said grooves respectively with end portions of the packs mounted in the grooves; and

cured adhesive material on each of said end portions of the packs combining with the end portion to form an enlargement filling the corresponding groove in dove-tailed engagement therewith, said adhesive material also defining means for bonding together end portions of the individual leaves of the pack and bonding the end portion of the pack to the inner surface of the groove to anchor the end portion of the pack in the groove and to prevent sliding movement of the end portion longitudinally of the groove.

9. A combination as set forth in claim 8 in which the end portion of each pack is constricted to fit snugly in the peripheral entrance of the corresponding groove of the hub structure with the leaves interlocked in the region of the restriction by penetration of abrasive particles of leaves into adjacent leaves.

10. A disposable flap-type abrasive Wheel, comprising:

a unitary hub structure having circumferentially spaced longitudinal grooves on its outer circumference with both ends of each groove open to the two opposite ends of the hub structure,

said grooves being undercut to form peripheral entrances thereto smaller in width than the maximum width dimension of the grooves;

packs of flexible abrasive leaves,

said packs corresponding to said grooves respectively with end portions of the packs extending into the grooves; and

cured adhesive material on said end portions of the packs combining with the end portions to form enlargements thereon shaped for interlocking engagement with the grooves,

said adhesive material on each of said end portions of the packs defining means for bonding together the inner ends of the individual leaves of the pack, said adhesive material further defining means for bonding the end portion of the pack to the inner surface of the corresponding groove to anchor the end portion of the pack in the groove and to prevent sliding movement of the end portion of the pack longitudinally of the groove out of either end of the groove thereby to avoid any necessity for mechanical barriers at the opposite ends of the groove to confine the end portion of the pack.

11. In a flap-type abrasive wheel wherein a hub structure has circumferentially spaced longitudinal grooves in its outer circumference with the radial entrances to the grooves smaller in width than the mam'mum width dimension of the grooves and wherein packs of flexible abrasive leaves have adhesive material at their inner ends bonding together the inner ends of the individual leaves, the adhesive material together with the inner ends of the leaves forming enlargements on the inner ends of the packs shaped for interlocking engagement with the grooves,

the improvement comprising said adhesive material defining means for bonding the inner ends of the packs directly to the inner surfaces of the grooves to resist radial withdrawal of the packs from the grooves and thus avoid depending solely on said interlocking engagement to resist radial withdrawal of the packs from the hub structure,

the adherence of the adhesive material to the inner surfaces of the grooves also defining means for preventing sliding movement of the end portions of the packs longitudinally of the grooves out of the ends of the grooves thereby to avoid any necessity for mechanical barriers at the opposite ends of the grooves to confine the end portions of the packs in the grooves.

' 12. An improvement as set forth in claim 11 wherein the grooves are of generally circular cross-sectional configuration.

References Cited UNITED STATES PATENTS 3,053,021 9/1962 Block 51-337 3,212,219 10/ 1965 Gillett 51-337 OTHELL M. SIMPSON, Primary Examiner 

